Flexor tendons repair: Effect of core sutures caliber with increased number of suture strands and peripheral sutures. A sheep model

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online

at

ScienceDirect

www.sciencedirect.com

Original

article

Flexor

tendons

repair:

Effect

of

core

sutures

caliber

with

increased

number

of

suture

strands

and

peripheral

sutures.

A

sheep

model

M. Uslu

a

_,

_C.

_Isik

b,∗

_,

_M.

_Ozsahin

c

_,

_A.

_Ozkan

d

_,

_M.

_Yasar

e

_,

_Z.

_Orhan

a

_,

M. Erkan

Inanmaz

f

_,

_H.

_Sarman

b

a_Düzce_University_Medical_School,_Department_of_Orthopaedics_and_{Traumatology,}_Düzce,_Turkey

b_Abant_Izzet_Baysal_University_Medical_School,_Department_of_Orthopaedics_and_{Traumatology,}_School_of_medicine,₁₄₂₈₀_Golkoy/Bolu,_Turkey c_Düzce_University_Medical_School,_Department_of_Physical_Treatment_and_{Rehabilitation,}_Düzce,_Turkey

d_Düzce_University,_Technology_Faculty,_Department_of_{Manufactering}_Engineering,_Düzce,_Turkey e_Düzce_University_Medical_School,_Department_of_General_Surgery,_Düzce,_Turkey

f_Sakarya_University_Medical_School,_Department_of_Orthopaedics_and_{Traumatology,}_Sakarya,_Turkey

a

r

t

i

c

l

e

i

n

f

o

Articlehistory: Accepted13May2014 Keywords:

Earlyactivemovement Flexortendoninjury Multi-strandsaturation Peripheralsuture Suturecaliber Flexortendonlaceration

a

b

s

t

r

a

c

t

Background: Surgeonshaveaimedtoachievestrongrepairsoastobeginearlyactiverehabilitation programsforﬂexortendoninjury.Multi-strandsuturetechniquesweredevelopedtogainimproved gapresistanceandultimateforcecomparedwiththerespectivetwo-strandtechniques.Invivostudies indicatethatmultiplestrandsmaycauseischemiaduringtheintrinsichealingprocessbydecreasingthe totalcross-sectionalareaoftheinjuredsite,unlessthetotalcross-sectionalareaofthesuturesisnot decreased.

Hypothesis:Thehypothesiswastodesignaninvitrostudytounderstandthebiomechanicalrelationship betweensuturecalibersofcoresutureswithincreasednumberofsuturestrandsandperipheralsuture onﬁnalrepairstrength.

Materials andmethods: Sixtyfresh sheep forelimb ﬂexordigitorum profundus tendonswere ran-domlyplacedintothreegroups(A,B,andC),eachcontaining20specimens,fortendonrepair.Two-, four-,andeight-strandsuturetechniqueswererespectivelyusedinGroupsA,B,andC.Asimplerunning peripheralsuturetechniquewasusedinSubgroupsA2,B2,andC2.Foreachrepairedtendon,the2-mm gap-formationforce,2-mmgap-formationstrength,maximumbreakingforceandmaximumbreaking strengthweredetermined.

Results:Differencesin2-mmgap-formationforceand2-mmgap-formationstrengthwerefoundbetween SubgroupsA1andA2,B1andB2,andC1andC2.BetweenGroupsAandB,AandC,andBandC,there wasnodifferenceaswell.

Conclusion:Boththenumberofstrandsandtheratiobetweenthetotalsuturevolumeandtendonvolume attherepairsiteareimportantforidealrepair.Ifthetotalcross-sectionalareaofthesuturesisequalin 2-strand,4-strand,and8-strandprocedure,thereisnodifferenceinthestrengthoftherepair.Adecrease incalibersizesuturerequiresmorepassestoachievethesamestrength.Instead,itismuchbettertouse peripheralsuturetechniquestoimprovethestrengthoftherepairwithlargerdiameter2-strandcore sutures.

1. Introduction

Primaryrepairof ﬂexortendoninjuries intheﬂexortendon sheathofthehandhasbeenreportedforthepastseveralyears

[1,2].Thegoalofﬂexortendoninjurytreatmentistoperforma

∗ Correspondingauthor.Tel.:+903742534656;Mobilephone:+905053835837. E-mailaddress:drcengiz034@yahoo.com(C.Isik).

strongrepairandbeginanearlyactiverehabilitationprogram.Early rehabilitationdecreasesadhesionformationandisrelatedtogood clinicalresults[3,4].Itisimportanttominimizefailureratesrelated tocomplications,suchasgap-formationorrupture.Primaryrepair mustbeperformedusingareliableandstrongsuturetechnique[5]. Flexortendonrepairtechniquesinvolvetheplacementofboth coreandperipheralsutures.Theinitialstrengthoftendonrepair iscloselyproportionaltothenumberofsuturestrandsthatcross therepairsite[6,7].Two-strandcoresutureandperipheralrepair

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Fig.1.Thediameterofthesutureswereinallgroups.

withrunningsutureswasmorecommonlypreviouslyused[1,8]. Applicationofasix-oreight-strandcoresutureprovidesgreater strengthbuthasthedisadvantageoftechnicaldifﬁculties. Multi-plestrandsmaytriggerischemiaintheintrinsichealingprocess becauseofadhesionformation[9].

Theaimofthisstudywastoevaluatethebiomechanical pro-pertiesoftwo-strand,four-strand,andeight-strandlockingcore suturetechniquesanda simplerunningperipheralsuture tech-niqueincombinationwithcoresutures.Wewereabletoassess themechanicaladvantagesoftechniquesbychangingthenumber ofstrandswithandwithoutperipheralsutures.Ourhypothesisis thatthenumberofstrandsandtheratiobetweenthetotalsuture volumeandtendonvolumeattherepairsiteareimportantforideal repair.Peripheralsuturesprovidemorestrengthinsuchcases. 2. Materialsandmethods

Atotalof60sheepforelimbsweredissectedtoobtainflexor digi-torumprofundustendons.Thisanimalmodelhasbeenreportedto bestmimichumanflexor tendonbiophysicalproperties[10,11]. Wemadetheexperiment daily; eachgroupfor oneday.Inthe firstdayforonlygroupA,tensheepsweresacrificed,tendonswere harvested,theywerekeptinsalinesolutionbeforeandafter sutu-rationsandtestingofthetendonswithtansiometer.Wedidthe samethingsforgroupBontheseconddayandforgroupConthe thirdday.

Thesheeps(averageage,8–10months)wereallhealthy and fromthesameherd,andtheyhadbeenkilledforcommercial pur-posesataslaughterhouse.Flexordigitorumprofundustendonsare ofthesamediameterasthatofﬂexortendonsinhumans.The ten-donswereapproximately7-to8-mmdiameter;themeanlength was10to12cm,andthemeancross-sectionalareawas23mm2_._All

repairswereperformedbythesamesurgeonusing4.0-loupe mag-niﬁcation(Heine,Germany)during3days(1dayforeachgroup). The60specimenswererandomlyplacedintothreeequalgroups

(A,B,andC)fortendonrepair.Eachgroupcontained20specimens. Eachwas groupdivided intotwo equal subgroups(A1, A2, B1, B2,C1,and C2),each containing10specimens.Two-,four-,and eight-strandsuturetechniqueswereappliedinGroupsA,B,andC, respectively.SubgroupsA1,B1,andC1hadnoperipheralsutures, whereasSubgroupsA2,B2,andC2werepreparedwithsimple run-ningperipheralsutures.Atransversesharpcutwasperformedin themid-portionofeachtendon,andtherepairwasthenperformed. SpecimensinGroupsA,B,andCwererepairedusing0-0,3-0,and 5-0monofilamentabsorbablecoresutures(monofilament polyg-lyconate;Maxon,Covidien),respectively,witha3/8cutting-edge needle.Invivo,polyglyconatedegradationtimeinthetendonis nearly180days.Asperipheralsuture,6-0polypropylene (monofil-amentpolypropylene;Surgipro,Syneture)witha3/8cutting-edge needlewasusedinsubgroupsA2, B2,andC2.Peripheralsuture peritendinousthrowswere2mmfromthelaceratedtendonends, with1to2mmbetweenthrows.Thetendonbitedepthwas approx-imately 1.5mm. The number of throws ranged from 10 to 14 accordingtothetendonsize.Thebasiccoresuturationtechnique wasmodified in Massachusetts GeneralHospital(MGH) repair, whichisalockedsuturetechnique[12].InoriginalMGH,suturesare lockedateachsideformorethanonethrow.However,wereduced thenumberoflockstooneoneachside.Foreverytwostrands, thesutureknotwastiedononesideoftheinjuredtendon;one, two,andthreeknotswereusedforGroupsA,B,andC,respectively. ThediameterofthesutureswasR(0.40–0.49mm)inGroupA,R/2 (0.20–0.24mm)inGroupB,andR/4 (0.10–0.12mm)inGroupC (Fig.1).Thedataweretakenfromthesuturemanufacturer com-pany.Thesuturetechnique,suturematerials,shapeoftheneedles, tendonquality,andtypeofknotstiedwereallthesame.Theonly differenceswerethenumberofstrandsthatcrossedtherupture siteandthediameterofthesutures.

Afterrepair,tendonswereverticallyheldinthenon-slipping jawsofsoft-tissueclampsmountedonatensiletestingmachine (Zwick, Germany). Two centimeters of the tendon were held

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Table1

Dataforeachtendonontensiletests.

Sectionarea(mm2₎ ₂_mm_gap_force_(n) _Max._breaking_load_(n) ₂_mm_gap_strength_(n/mm2) _Max._strength_(n/mm2₎ _Info

A1 21 30 141 1.429 6.714

A1 22 24 128 1.091 5.818

A1 16 20 99 1.250 6.188

A1 28 18 83 0.643 2.964

A1 23 12 20 0.522 0.870

A1 27 9 0 0.333 0.000 Failedtiedknotsecurity

A1 31 0 85 0.000 2.742 Pulledout

A1 31 15 64 0.484 2.065

Means±A1 23.5 19.83±6.46 89.17±44.15 0.90±0.40 4.10±2.45 A2 23 80 84 3.478 3.652 A2 28 64 72 2.286 2.571 A2 24 22 0 0.917 0.000 Pulledout A2 22 41 0 1.864 0.000 Pulledout A2 24 80 89 3.333 3.708 A2 24 59 55 2.458 2.292 A2 22 85 89 3.864 4.045 A2 15 79 80 5.267 5.333 A2 27 59 60 2.185 2.222 A2 25 67 72 2.680 2.880 Means±A2 23.5 71.63±10.50 75.12±12.76 3.19±1.03 3.33±1.05 B1 24 40 95 1.667 3.958 B1 22 10 105 0.455 4.773 B1 16 14 130 0.875 8.125 B1 18 15 36 0.833 2.000 Pulledout B1 22 14 40 0.636 1.818 B1 28 22 134 0.786 4.786 B1 19 19 26 1.000 1.368 Pulledout B1 22 14 35 0.636 1.591 Pulledout B1 24 24 70 1.000 2.917 B1 25 7 70 0.280 2.800 Means±B1 23.00 18.71±11.17 92.00±34.29 0.81±0.44 4.16±1.77 B2 29 43 0 1.483 0.000 Pulledout B2 21 40 40 1.905 1.905 B2 19 83 97 4.368 5.105 B2 24 113 113 4.708 4.708 B2 25 53 90 2.120 3.600 B2 26 96 110 3.692 4.231 B2 19 101 101 5.316 5.316 B2 19 84 127 4.421 6.684 B2 21 118 170 5.619 8.095 B2 19 79 79 4.158 4.158 Means±B2 21.44 85.22±25.83 103.00±35.2 4.03±1.28 4.86±1.77 C1 21 30 141 1.429 6.714

C1 22 24 128 1.091 5.818 Suturecuttendonmatrix

C1 16 20 99 1.250 6.188

C1 28 18 83 0.643 2.964

C1 23 12 20 0.522 0.870 Suturebroken

C1 27 9 11 0.333 0.407 Suturebroken

C1 29 9 0 0.310 0.000 Suturebroken C1 31 15 64 0.484 2.065 C1 18 7 18 0.389 1.000 Suturebroken Means±C1 23.6 21.40±5.81 103.0±31.64 0.97±0.40 4.74±2.08 C2 23 80 84 3.478 3.652 C2 28 64 72 2.286 2.571

C2 24 80 89 3.333 3.708 C2 24 59 59 2.458 2.458 C2 22 85 89 3.864 4.045 C2 15 79 80 5.267 5.333 C2 27 59 60 2.185 2.222 C2 25 67 72 2.680 2.880 Means±C2 23.5 71.63±10.50 75.63±11.91 3.19±1.03 3.35±1.03

each the jaws. The lengthof therepaired tendonbetweenthe

two jaws was 6cm, and the repaired zone was in the middle

(Fig.2).Apre-loadof4N wasapplied.Alltendonswere subse-quentlyloadedtothefailurepointatastaticrateof2mm/s,and

force-versus-displacement data were recorded. The 2-mm gap-formation force, 2-mm gap-formation strength, maximum breaking force, maximum strength, and maximum elongation weredeterminedforeachtendon.Alldatawererecorded(Table1).

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Fig.2.Thetendonwascompressedbetweentensilemachinesawsbythinﬁne sandpapers.

2.1. Statisticalanalyses

ThedatawereanalyzedusingStatisticalPackageforSocial Sci-encessoftware(SPSS® 14812;SPSS,Inc.,Chicago,IL,USA).The distributionofthedataineachgroupwasevaluatedbythe Shapiro-Wilktest. The datain three ormore independentgroups were compared using the Kruskal-Wallis test. Multiple comparisons wereperformedusingtheBonferroniadjustedMann-Whitney U-testtodeterminedifferencesamonggroups.Thecontinuousdata arepresentedasmean±standarddeviation.AP-valueof<0.05was consideredsigniﬁcant.

3. Results

Initially,60tendonswereincludedinthestudy.Someofthe tendonswereexcludedaftervariousproblemswereencountered

duringtensiletesting.Theseproblemswerelooseningofthetied knots,slippingofthetendonendsfromthetensilemachinejaws, andlacerationofthetendonsbythesutures.Attheendofthestudy, 43tendonshadbeenstatisticallyevaluated.

Cross-sectionalareaswerecalculatedwithgraphpaperprinting method.Theaveragecross-sectionalareaforasampleof43tendons was23.01mm2_(minimum,₁₅_mm2_;_maximum,₃₁_mm2_).

Statis-tically signiﬁcant differences in the 2-mm gap-formation force and2-mmgap-formationstrengthwerefoundbetweensubgoups A1and A2,B1andB2,andC1and C2(P<0.05).No statistically signiﬁcantdifferences in the 2-mm gap-formation force, maxi-mumbreakingforce,2-mmgap-formationstrength,andmaximum breakingstrengthwerefoundbetweensubgroupsA1andB1,A1 andC1,B1andC1,A2andB2,A2andC2,andB2andC2(P>0.05). Statisticalanalyseswereshownwithgraphics(Fig.3).

4. Discussion

Thisstudy, based onthe hypothesis that the biomechanical strengths of two-strand, four-strand, and eight-strand locking core suturetendon repair techniques are identical, showed no signiﬁcant differences among these techniques when the total cross-sectional areaof thesutures joining theinjured edgesof thetendonswasequal.Theaimofthisstudywastocomparethe biomechanicalpropertiesoftechniquesincombinationwithcore sutures.A simple runningperipheralsuturetechnique provides greaterstrengthintendonrepair[13].

Thestrengthandstiffnessoftherunningperipheralsuturecan beincreased withdeepersuture grasps[14],by increasingthe suturepurchasefrom1to2or3mm[15],andbyincreasingthe numberofsuturepasses[16].Peripheralsutureisusednotonly intotalruptures,itisalsousedinpartialrupturestosupportcore sutureifthecross-sectionexceeds50%aswell[17].Inthestudy, peripheralsutureincreased,especially2-mmgap-formationforce and2-mmgapstrengthineachgroup.Peripheralsuturesarean importantcomponentofﬂexortendonrepairandcontribute sig-niﬁcantlytothestrengthoftherepair.

Flexortendonrepairstudieshavereportedonthedirecteffects ofthetypeanddiameterofthesuturematerial,suturetechnique, and number of strands onthe strength of the repair. With an

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increasednumberofcoresuturestrands,thestrengthoftherepair improvesifthediameterofthesutureisstableandthetotal cross-sectionalareaisincreasedwiththeincreasednumberofstrands. Therefore,sixstrand[18,19]andeight-strand[20,21]coresuture techniqueshavebeendeveloped.Additionally,withanincreased numberofcoresuturestrands,thecross-sectionalareaoftherepair siteincreases,andtheexcursionofthetendondecreases,in addi-tiontoothertechnicaldifﬁculties[18,20].

Severalin vitro studieshave confirmedthe superior tensile propertiesofmulti-strandcoresutures[22,23].However,concerns regardingtechnicaldemandsandskillacquisition,repairbulk,and longeroperatingtimes[24]mayreducetheclinicalfeasibilityand limittheusemulti-strandcoresutures.Inourstudy,variationsin thecoresuturemethod(two-,four-,oreight-strands)didnot sig-nificantlyaffectenergyvaluesinthetensiletest,suggestingthatthe numberofcoresuturestrandshasnoeffectontheenergyoffailure oftenorraphy.Thediameterofthesuturesdecreasedasthe num-berofsuturestrandsincreased.Despitenumerousinvestigations oftendonrepairtechniques,onlyafewhavefocusedontheeffect ofsuturecaliberonthebiomechanicalpropertiesofflexortendon repairs.Increasingthesuturecaliberhasbeenshowntoincrease theultimateforceinstatictesting[25,26]andfatiguestrengthin dynamictesting[8].However,ithasnotbeenshowntoimprove theyieldforceorgapresistanceoftherepairs.

Gap-formationleadstoadhesionsattherepairsite[27]. Clini-cally,evaluationofthe2-mmgap-formationforceismoreuseful thanevaluationofultimatetensilestrength[1,28,29].The mech-anismsof failureweredifferentforeachcoresuturetechnique. Intendonsrepairedusingthetwo-strandcoresuturetechnique, thesutureinitiallypulledout,leavingoneofthetwoends.Asthe diameterofthesutureincreased,thetiedknotsecuritydecreased, andthesuturepulled out.In tendonsrepaired usingthe eight-strandcoresuturetechnique,thesuturehadlowtensilestrength and2-mmgap-formationstrength.Asthediameterofthesuture decreasedandthesuturebecamethinner,thesuturewasbrokenat somepointbyfurtherelongationofthetendon,orthesuturecutthe tendonmatrix,causingfailure.Thismaybeduetothestrong grasp-ingandholdingofthetendonbythelockingsutures,sothatthe graspingstrengthofthesutureseemsstrongerthanthestrengthof thematerial.

Two-strandrepairtechniqueshavegenerallybeenusedinflexor tendonrepair.Thesetechniquesarestrongenoughtowithstand theforcesofpassiverehabilitation,butnotthoseassociatedwith earlyactive motion;clinically this is seen in increasedrupture rates[30].Multi-strandsuturetechniquesweredevelopedtogain improvedgapresistanceand ultimateforcecompared withthe respectivetwo-strandtechniques.Multi-strandrepairstechnically requiremultipleconsecutiveneedlepasses,whichincrease ten-donhandlingandeasilyleadtoloadingofthestrands.Multiple concomitantlypassed suturestrands have been investigatedto improvetheholdingcapacitywithasimplerrepairtechnique.The technicaldifficultyinthiscasewasthatthetendonvolumewasthe same,andthesuturevolumesubstitutedfortendonvolumewith increasingnumbersofstrands.Toavoidthisproblem,wedecreased thediameterofthesutureeachtimeweincreasedthenumberof strands.Asaresult,ineachtechnique,thetotalcross-sectionalarea ofthesuturesandtheratiobetweensuturevolumeandtendon vol-umewerenearlyequal.Thetiedknotswereplacedontheoutside inallcases.Loopconfigurationandcoresuturepurchasedwereall identical.Theonlyvariabilitywasinthenumberofstrandsandthe diameterofthesutures.

Clinical and experimentalstudies have shown that to mini-mizefailureratesrelatedtocomplicationsoccurringduringactive rehabilitation,suchasgap-formationorrupture,itiscrucialthat primary repair is performedusing a reliable and strongsuture technique[5,31].Thisstudyalsohasseveralpotentiallimitations.

Adhesionandtendonhealingpotentialcouldbeevaluatedin exper-imentalstudywithliveanimalmodel.Inthefuturestudieswillbe neededtoperformthistechniquewithlargenumbersoflive ani-malsineachgroups.Ininvivostudies,itwilltakelongoperation time toperformmulti-strandsuturetechniqueasdisadvantage. Therewere somesubjective negative resultswith multi-strand suture techniquessuchas cutting of tendonmatrix by thinner suturesandbrokensutures.

5. Conclusion

Multi-strand suture techniques have become popular since earlyactive-movementprotocolswerebeguninrehabilitation pro-grams.Thisstudyrevealedthatboththenumberofstrandsandthe ratiobetweenthetotalsuturevolumeandtendonvolumeatthe repairsiteareimportantforidealrepair.Thediameterofthesuture decreasedasthenumberofsuturestrandsincreased.Inthiscase,it ismuchbettertouseperipheralsuturetechniquestoimprovethe strengthoftherepairwithlargerdiameter2-strandcoresutures. Disclosureofinterest

Theauthorsdeclarethattheyhavenoconﬂictsofinterest con-cerningthisarticle.

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